Pretty cool stuff: the PlayStation 4 apparently runs on a version of FreeBSD 9.0 modified by Sony and renamed to 'Orbis OS'. Second generation developer kits use GNU GRUB to boot, and allow you to boot into a graphical or a console mode. Not much else is known at this point, but it's a fun bit of information, and perhaps a boon to homebrew developer and hackers.

There is a discussion on this topic over in the FreeBSD forums and it looks as though some of the code is being contributed back to the FreeBSD project. Which makes sense, rolling the changes back into FreeBSD means Sony doesn't have to maintain a large fork, contributing means less work for them in the long run.